Conveying of plastic bottles

ABSTRACT

A conveying system ( 1 ), comprising a modular conveyor belt ( 2 ) supported on a conveyor track ( 3 ) so that top surfaces ( 4 ) of the modules ( 5 ) of the conveyor belt present a conveying face ( 6 ) that in use moves along the track in a conveying direction, and at least one plastic bottle supported at its bottom on the conveying face via one or more textured surfaces at a bottom of the bottle. The disclosure also includes a method of conveying bottles, wherein plastic bottles are supported with their bottoms on a moving conveying face of a conveyor, and wherein the conveying face and the bottom of the bottle are conveyed via one or more textured surfaces ( 12 ) at a bottom of the bottle. The disclosure further includes use of at least one textured bottom surface of a plastic bottle for conveying, and a blow mold for blow molding a plastic bottle.

The invention relates to conveying plastic bottles.

Plastic bottles are widely used to package products, and are in someindustries even amongst the most common packaging forms. For example, inthe beverage industry, one of the most common packaging forms for homeconsumption of soft drinks is bottling in PET bottles. PET bottles arestrong, light weight and offer good recyclability. The bottles are oftenblow molded from preforms, and typically include a number of downwardlyprojecting feet at their bottoms. Plastic bottles are often thin walled,e.g. with a wall thickness between 0.1 and 2 mm, and have volumesranging e.g. from 0.1 to 5 liters.

When handling plastic bottles, e.g. for bottling or labelling, bottlesare often moved along by conveying, both in empty or filled condition.Typically, the bottles are then supported with their bottoms on a movingconveying face of the conveyor. The bottles may be conveyed in bulkalong wide conveyor tracks, at relatively low speed with several bottlesnext to each other, e.g. to or from a buffer zone. The bottles may attimes also be conveyed single file at relatively high speed, e.g. to orfrom a labelling or filling station. The bottles are typically guidedalong the conveying face using guide rails, e.g. to follow a curved pathor to transfer between conveyors. Bottles on the conveying face thus attimes need to accelerate, decelerate or change direction relative to theconveying face.

Bottles typically have a height that is greater than the maximum crosssectional dimension, e.g. a height that is at least 2 or 3 times thediameter. Due to the bottles being relatively tall compared to theirdiameter, care should be taken that the movement relative to theconveying face does not cause the bottle to topple over. This is inparticular the case when the bottles are conveyed using a modularconveyor of which the conveying face is potentially less smooth as it isnot integrally formed, but made up of the top surfaces of individualconveyor modules. Especially when the bottles are without support ofneighboring bottles, it can be very difficult to keep the bottles fromtoppling over. Toppling over of a single bottle on a conveyor may resultin large numbers of bottles toppling over, and to the bottles becomingdamaged.

For dependable conveying of bottles, it is therefore desirable to have arelatively low, and reliably constant friction between the bottom of thebottle and the conveying face. In practice, external lubricants areprovided to the conveying face, e.g. Teflon or silicone based dry,semi-dry or liquid lubricant. Also, soap or oil based liquid lubricantsare used lubricant.

From a handling point of view, it is however much preferred if thebottles could be conveyed without such external lubrication. This,however, poses problems of too much friction. Especially when theconveying face includes a plastics material, adhesive contact may occurdue to polarity of both the bottle and the conveyor material.

To reduce friction, it has been proposed to provide the top surfaces ofconveyor modules with projections, for example as described in WO96/41759 and DE 102011114250. Such projections or other structuresreduce the actual contact area between the bottles and the conveyingface, which reduces adhesive contact and friction. In practice, however,such a textured conveying face becomes dirty and is prone to wear, andcan therefore not offer the reliably constant low friction that isoffered by a lubricated conveying face.

The invention aims to alleviate the above disadvantages. Thereto theinvention provides for conveying of plastic bottles with their bottomssupported on a conveying face of a conveyor via one or more texturedsurfaces provided at a bottom of the bottle. By providing the texturedsurface(s) at the bottom of the bottle, it can be ensured that the oneor more textured surfaces are relatively fresh and clean duringconveying. This because in the conveying process, the bottles are onlyconveyed for a relatively short period of time compared to the standingtime of the conveyor belt, so that during conveying in practicedeterioration of a textured surface at the bottom of a bottle isminimal. For example, in a typical bottling process a bottle may beconveyed on the conveying face for several minutes or typically lessthan an hour, whereas the standing time of the conveying face istypically more than a year, or at least more than a month. Not only doesthe provision of a textured surface profile on the bottom of the bottleprovide for predictable and well controlled friction, it also allows thesurface of the conveyor to be optimized for other parameters thanfriction. For example, the top surfaces of modules making up theconveying face may de designed to be flat and smooth to achieve optimumcleanability and/or strength of the surface. The textured surface(s) atthe bottom of the bottle may form a contact reducing surface profilesuperposed on the bottom wall of the bottle to provide a reliably lowand constant coefficient of friction during conveying. Typicalcoefficients of friction between the conveying face and the texturedsurface(s) provided at the bottom of the bottle range between 0.06 and0.18, in particular between 0.07 and 0.16, more in particular between0.08 and 0.12, without external lubrication. The provision of thetextured surface(s) is an adaptation that has little impact onmanufacturing, appearance or consumer use of the bottle, yet it solves abig problem in conveying the bottle.

Within the context of this patent specification, the term ‘texturedsurface’ is to be construed as a surface portion that is rough comparedto an adjacent surface portion of the bottle. Such adjacent surfaceportion may in particular have a surface finish that is smooth comparedto the textured surface. Such adjacent surface portion may in thecontext of this application then in particular be considered anon-textured surface. Such a smooth surface may, as a matter ofreference, as smooth as a regular wall of a typical plastic bottle. Thetextured surface may thus be rough compared to a surface having thenormal surface finish of the walls of a conventionally blow moldedstandard commercial 1.5 litre Coca Cola PET bottle as currentlyavailable in supermarkets in The Netherlands. Such adjacent surface maytypically be an adjacent surface on the bottom of the bottle. In case ofa bottle made of a transparent or translucent material, such texturedsurface may cause the surface to be opaque, while the adjacent,non-textured surface may be clear.

The at least one bottle may as mentioned above be supported on theconveying face via the textured surface(s) free of external lubricationbetween the bottle and the conveying face. It should be noted that, ifdesired, some external lubrication may still be provided, e.g. water orsome moisture. Further, it should be noted that internal lubrication maybe provided, e.g. lubricants included in the material of the plasticbottle or plastic conveyor modules.

In particular, the invention provides for a conveying system, comprisinga modular conveyor belt supported on a conveyor track so that topsurfaces of the modules of the conveyor belt present a conveying facethat in use moves along the track in a conveying direction, and at leastone plastic bottle supported at its bottom on the conveying face via atleast one textured surface at a bottom of the bottle. Preferably, theconveying system includes a plurality of plastic bottles supported onthe conveying face, each bottle including said textured surface(s).

The bottle, especially the bottom of the bottle, may be provided withone or more base surfaces that face a supporting surface such as a tabletop or conveying face, when the bottle stands upright. The base surfacemay form, comprise or be part of the textured surface. Said one or morebase surfaces can be located in a lowermost outer boundary of thebottle. In embodiments, said lowermost outer boundary of the bottle canfor instance be formed by a substantially flat portion of the bottomwall of the bottle, which in that case can form a relatively large basesurface. However, in other embodiments, the bottom wall of the bottlecan for instance be provided with downwardly projecting support feet,wherein lowermost end faces of the support feed can form base surfaceson which the bottle can be supported.

The one or more base surfaces may each have a surface area of severalcm² or less, e.g. less than 1 cm², or less than 0.5 or 0.2 cm² per basesurface.

In preferred embodiments, the one or more base surfaces of the bottlemay combined cover a surface area being substantially smaller than thelargest horizontal cross-sectional area of the bottle. For example, the(combined) surface area covered by the base surface(s) can be less than70% of the cross-sectional area of the bottle, preferably less than 50%or 30%, especially less than 20% or 10%, for instance less than 5% or2%, or even less than 1% or 0.5%.

The base surface(s) may be provided with projections and may form thetextured surface(s) at the bottom of the bottle.

The textured surface(s) at the bottom of the bottle may includeprojections that project from a respective base surface at the bottom ofthe bottle, and the projections may engage the conveying face to formtogether a combined contact area that is smaller than a base area of theengaged projections, i.e. an area covered by the one or more basesurfaces from which the engaged projections project. The engagedprojections may each have an individual contact area of several mm² orless, e.g. less than 1, 0.5 or 0.1 mm², or less than 0.05, 0.02 or 0.01mm² per projection. The combined contact area of the engaged projectionsmay be less than 50% of the base area of the projections, preferablyless than 30% or 20%, for instance less than 10% or 5%, or even lessthan 2% or 1%. The projections may be spaced apart from each other overless than 1 mm, e.g. less than 0.5 or 0.2 mm, or even less than 0.1 or0.05 mm, measured center to center. The projections may successfully beformed as microstructures having dimensions and/or spacings in the rangeof tenths of millimeters. The engaged projections of the texturedsurface at the bottom of the bottle that cooperate with the conveyingface when the bottle stands on the conveyor may have a total contactarea that is less than 0.5%, preferably less than 0.2 or 0.1% of thearea of projection of the bottle along its upright axis onto theconveying face, i.e. the maximum cross sectional area of the bottlealong its height. By providing the textured surface onto support feet ofa bottle, the already very minimal actual contact area of non-texturedsupport feet may be reduced significantly further to be e.g. half or1/10^(th) of the actual contact area of the non-textured support feet,without significantly reducing the stability of the bottle.

The textured surface(s) may be provided on the bottom of the bottle,e.g. on the bottom wall of the bottle or on a bottom cap of the bottle.In case the one or more base surfaces are part of a bottom wall of thebottle, no auxiliary structure is needed on the bottom of the bottle.The textured surface(s) may also be provided on an auxiliary structureor part that at least during conveying forms the bottom of the bottle,e.g. on a skid plate or sticker attached to the bottom of the bottle,especially to the feet of the bottle.

The textured surface(s) may include projections or structural elementsprojecting from a respective base surface, e.g. intersecting orconcentric ridges, lands between grooves, nodules, tears, prisms,pyramids, hemispheres, dimples, or may each just be formed as a roughsurface to provide a friction reducing surface profile. The texturedsurface(s) at the bottom of the bottle may be provided directly on thebottom itself, e.g. by removing, displacing or adding material, or maybe transferred thereon via a transfer process, e.g. molding. The surfacetexture or its mirrored image in case of a mold may e.g. be providede.g. by electronic discharge machining (EDM), abrasion, chemical milling(CM), engraving, embossing, etching, milling, cutting, sandblasting,impacting or other technique to form a contact reducing surface profile.The texture may be patterned or may be random.

The textured surface(s) may be provided at the base surface(s), e.g. atthe ends of support feet projecting downward at the bottom of thebottle. This way, the textured surface(s) can be provided only therewere it/they is/are needed for reducing friction during conveying, andneed not or hardly influence the appearance of the bottle.

If desired, the textured surface(s) may be removed or smoothened afterconveying, e.g. in a polishing step.

Preferably, the textured surface(s) can comprise polyethyleneterephthalate (PET). PET is a material with which the coefficient offriction on a steel or plastic conveying face may be reduced andmaintained at a controlled, desirably level for conveying the a bottlethrough a regular packaging process that includes e.g. bottling,labelling and batching into transport groups. The textured surface(s)may be made of PET, and advantageously, the bottle may comprise or maybe made of PET.

When the top surfaces of the modules conveyor are made of plastic, e.g.a hard, strong and/or wear resistant plastic, e.g. POM, PA, or PBT, thetextured surface(s) may be especially useful to bring friction for thebottle to a desirable low level without external lubricant.

The modular conveyor belt may be arranged to recirculate between firstand second divert elements, a top run of the conveyor extending betweenthe first and second elements and being supported on a conveyor track,so that in the top run, top surfaces of the modules of the conveyor beltpresent a conveying face that in use moves in a conveying direction fromthe first divert elements towards the second divert element. Theconveying system may comprise a plurality of plastic bottles, eachsupported at its bottom on the conveying face via one or more texturedsurfaces at the bottom of the bottle.

The invention also provides for a method of conveying bottles, with useof a conveying system as discussed above or without, wherein plasticbottles are supported with their bottoms on a moving conveying face of aconveyor, and wherein the conveying face and the bottom of the bottleare conveyed via one or more textured surfaces at a bottom of thebottle. In addition, the invention also provides for the use of at leastone textured bottom surface of a plastic bottle for conveying. Further,the invention provides for a blow mold for blow molding a bottle,including at least two mold parts that in a closed position cooperate toform a cavity defining the outer shape of a bottle, and in an openposition allow a bottle to be taken out of the cavity, and positioningmeans for positioning a preform to a bottle, wherein the cavity isprovided with a counter form for providing a textured surface at a partof the cavity corresponding to the bottom of the bottle to be formed.The invention also relates to a plastic bottle provided with one or moretextured conveying surfaces at the bottom.

It should be noted, that the steps and technical features describedherein may each on its own be embodied in a method of conveying orconveying system, i.e. isolated from the context in which it isdescribed, separate from other steps or features, or in combination withonly a number of the other steps or features described in the context inwhich it is disclosed. Each of these steps or features may further becombined with any other step or feature disclosed, in any combination.

The invention will be further elucidated on the basis of anon-limitative exemplary embodiment which is represented in a drawing.In the drawing:

FIG. 1 shows a schematic perspective view of a conveying systempresenting a conveying face comprising a plurality of plastic bottles,each supported at its bottom on the conveying face via one or moretextured surfaces at the bottom of the bottle,

FIG. 2 shows a schematic perspective bottom view of a plastic bottle ofthe system of FIG. 1, and

FIGS. 3a-3e show a detail of the bottle of FIG. 2 including one of itstextured surface.

It is noted that the figures are merely schematic representations of apreferred embodiment of the invention. In the figures, identical orcorresponding parts are represented with the same reference numerals.

FIG. 1 shows a conveying system 1. The conveying system comprises amodular conveyor belt 2 supported on a conveyor track 3. Top surfaces 4of the modules 5 of the conveyor belt 2 present a conveying face 6. Theconveying face 6 in use moves along the track 3 in a conveyingdirection, indicated with arrow P. The modular conveyor belt 2 istypically arranged to recirculate between first divert elements andsecond divert elements. A top run 9 of the conveyor belt 2 then extendsbetween the first and second elements and is supported on the conveyortrack 3. The conveying face 6 in use moves in the conveying direction Pfrom the first divert elements towards the second divert elements. Themodules 5 of the conveyor belt 2 are in this example made of plastic,and can be injection molded, e.g. from PBT, and the top surfaces of themodules can be provided with a smooth, substantially flat non texturedsurface.

The conveying system comprises a plurality of plastic bottles 10. Eachbottle is supported at its bottom 11 on the conveying face 6 via anumber of textured surfaces 12 at the bottom 11 of the bottle 10.Although the bottle 10 in the embodiments shown here comprises fivetextured surfaces 12, alternative bottles can comprise more or less thanfive textured surfaces, e.g. one, two, four or six textured surfaces.The bottles 10 are in this example supported on the conveying face 6 viathe textured surfaces 12 free of external lubrication between the bottle10 and the conveying face 3, i.e. without added lubrication. Hence,dirtying the conveyor system 1, e.g. its conveyor belt 2 and/or dirtyingthe bottles 10 can be counteracted.

The bottles 10 in this example are made of PET, and have been blowmolded in a mold from a standard injection molded preform. The bottlesin this example are 1.5 l carbonated soft drink bottles having a heightof about 30 cm, and a base diameter of about 8 cm. The bottles are thinwalled, and have a wall thickness of about 0.8 mm at the bottom, andhave a volume of 1.5 l. The bottles 10 include downwardly projectingfeet 13 at their bottoms. The blow mold used for blow molding thebottles includes two mold halves. In a closed position the mold halvescooperate to form a cavity defining the outer shape of a bottle, and inan open position they are spaced apart to allow a bottle to be taken outof the cavity. In the closed position of the mold, the preform ispositioned within the mold cavity, and positioning means position thepreform in the cavity, so that it can be blown against the cavity wallsto form a bottle. The cavity is provided with a counterformed, invertedtexture at a the bottom of the cavity, so as to provide a correspondingtextured surface at the bottom of the feet 13 of the bottle 10 to beformed. The texture may be provided in the mold cavity using electronicdischarge machining.

The textured surface 12 is in the example integrally formed with thebottom wall 14 of the bottle 10, and is provided at the extremities ofsupport feet 13 projecting downward at the bottom 11 of the bottle 10.

As can be seen in FIGS. 3, in particular FIG. 3e , the textured surface12 includes projections 15 that project from a base surface 16 at thebottom 11 of the bottle 10. The projections 15 are designed to engagethe conveying face to together form a combined contact area that issmaller than a base area of the engaged projections, i.e. an areacovered by the base surface 16 from which the projections 15 project. Inuse, fresh plastic bottles 10 are placed on the top run 9 of theconveyor belt 2, and are conveyed in the conveying direction P. Theplastic bottles 10 are supported with their bottoms 11 on the movingconveying face 6 of the conveyor 2, and are conveyed via the texturedsurfaces 12 at the bottom 11 of the bottle 10. The textured surfaces arerelatively fresh and clean during conveying. This because in theconveying process, the PET bottles are for example only conveyed for1-10 minutes on the conveying face 6 formed by the flat, smooth topsurfaces 4 of the plastic conveyor modules 5, so that during conveyingdeterioration of the textured surfaces 12 at the bottom 11 of eachbottle 10 is negligible, and the coefficient of friction remainsconstant at about 0.06-0.18. The friction between the bottles and theconveying face can thus be reliably constant and low, without need forexternal lubrication.

The invention is not limited to the exemplary embodiment representedhere. For example, the conveyor belt may be embodied as a mat or chain,and may even be of continuous, non modular construction. In addition,the conveyor belt may be part of a series of conveyor belts in thesystem. The conveyor belt may be made of hard material, e.g. steel orhard plastic, but may also be made of resilient material, e.g. rubber orelastomer. The bottles may have various shapes and sizes, and may bemade of many different types of plastic materials, or compositionsincluding plastic. Such variations shall be clear to the skilled personand are considered to fall within the scope of the invention as definedin the appended claims.

LIST OF REFERENCE SIGNS

1. Conveying system

2. Modular conveyor belt

3. Conveyor track

4. Top surface of module

5. Module

6. Conveying face

7. First divert elements

8. Second divert elements

9. Top run

10. Plastic bottle

11. Bottom

12. Textured surface

13. Support foot

14. Bottom wall

15. Projection

16. Base surface

P. Conveying direction

1. A conveying system, said conveying system comprising: a plurality ofmodules forming a modular conveyor belt supported on a conveyor track sothat top surfaces of the modules of the conveyor belt present aconveying face that in use moves along the track in a conveyingdirection; and at least one plastic bottle, said at least one plasticbottle having at least one textured surface and being supported on theconveying face via said at least one textured surface at a bottom of thebottle.
 2. The conveying system of claim 1, wherein the at least oneplastic bottle is supported on the conveying face via the at least onetextured surface free of external lubrication between the at least oneplastic bottle and the conveying face.
 3. The conveying system of claim1, wherein the at least one textured surface includes projections thatproject from one or more base surfaces at the bottom of the at least oneplastic bottle.
 4. The conveying system of claim 3, wherein theprojections engage the conveying face to form together a combinedcontact area that is smaller than a base area of the engagedprojections.
 5. The conveying system of any of claim 2, wherein the oneor more base surface are part of a bottom wall of the at least oneplastic bottle.
 6. The conveying system of any of claims 1, wherein theat least one textured surface is a plurality of textured surfacesprovided at ends of support feet projecting downward at the bottom ofthe at least one plastic bottle.
 7. The conveying system of claim 1,wherein the at least one textured surface includes polyethyleneterephthalate (PET).
 8. The conveying system of claim 1, wherein the topsurfaces of the modules are made of plastic.
 9. The conveying system ofclaim 1, wherein the top surfaces of the modules are provided with asmooth, nontextured surface.
 10. The conveying system of claim 1,wherein the modular conveyor belt is arranged to recirculate betweenfirst and second divert elements, a top run of the conveyor extendingbetween the first and second elements and being supported on theconveyor track, so that in the top run, top surfaces of the modules ofthe conveyor belt present the conveying face that in use moves in theconveying direction from the first divert elements towards the seconddivert elements.
 11. A method of conveying bottles, said methodcomprising: supporting at least one plastic bottle on a moving conveyingface of a conveyor, said at last one plastic bottle having at least onetextured surface, wherein the at least one plastic bottle beingsupported on the conveying face via said at least one textured surfaceat a bottom of the bottle.
 12. The method of claim 11, wherein the atleast one plastic bottle is conveyed without external lubricationbetween the at least one plastic bottle and the conveying face. 13.(canceled)
 14. A blow mold for blow molding a bottle, said blow moldcomprising: at least two mold parts that in a closed position cooperateto form a cavity defining an outer shape of a bottle, and in an openposition allow a bottle to be taken out of the cavity, wherein thecavity is provided with a counterform for providing a textured surfaceat a part of the cavity corresponding to a bottom of the bottle to beformed.
 15. The method of claim 11, in which said conveyor is a modularconveyor belt formed from a plurality of modules supported on a conveyortrack so that top surfaces of the modules of the conveyor belt presentthe conveying face that in use moves along the track in a conveyingdirection.